Shock pulsed rotary drill bit



April 19, 1955 BQUCHER 2,706,618

SHOCK PULSED ROTARY DRILL BIT Filed July 28, 1953 FRANK G. BOUCHERINVENTOR y Z0, 0. 7 ATTORNEY United States Patent SHOCK PULSED ROTARYDRILL BIT Frank G. Boucher, Tulsa, Okla., assignor to Esso Research andEngineering Company, a corporation of Delaware Application July 28,1953, Serial No. 370,782

5 Claims. (Cl. 255-300) The present invention is concerned with animproved method and apparatus for drilling well bore holes. Theinvention more specifically relates to an improved method of rotarydrilling particularly when utilizing a rock bit. In accordance with thepresent invention, rock formations encountered in a drilling operationare subjected to alternating stresses in a manner to cause fatigue andfailure of the rock. This is accomplished in accordance with the presentinvention, by utilizing circulating pellets at the bottom of the drillstring in conjunction with the bit. The impact of the pellets serves toprovide percussion forces which are transmitted to the bit.

In the exploration for oil, the art of drilling well bore holes intosubterranean areas of the earth has been widely investigated andextensively developed. The techniques employed are many and a widevariety of drilling bits and associated apparatus have also beendeveloped. One conventional procedure is to attach a suitable bit on theend of a pipe string and to rotate the bit by the rotation of the pipestfing.

Thus, at the present time, the majority of drilling operations areconducted by employing rotary drilling equipment. In conventional rotarydrilling, a hollow jointed steel shaft called the drill stem is rotatedfrom the surface of the earth. This shaft, extending downwardly into theearth to any desired depth, rotates a drill bit. For a number of reasonsthere are attached to the lower end of the drill pipe, heavy sections ofpipe termed drill collars. Also, for a number of purposes, a weightedfluid called drilling mud is circulated in one direction through thedrill stem and in the opposite direction through the annulus between thedrill stem and the bore hole.

In these drilling operations, it is known that rocks subjected toalternating stresses will fail rapidly in fatigue. This effect isresponsible to some extent for the action of conventional rock bits,wherein toothed cutters rolling on the surface of the rock impartalternating stresses to the surface of the rock, resulting in chipping,fracturing, and crumbling of the rock being drilled. The conventionalrock bit, however, depends to a very great extent for its cutting actionupon compressive stress induced by excessive weight on the bit. This issecured by allowing the weight of the drill string to partially rest onthe bit. This process while entirely satisfactory has a number ofinherent difficulties. For example, part of the drill pipe may be incompression resulting in buckling of the pipe which in instances causesthe hole to deviate from the vertical. Furthermore, the stress induceddue to the buckling and unbuckling of the compressed pipe results incorrosion fatigue. To reduce this difliculty, drill collars, which areheavy lengths of pipe, are used. These are expensive, and are subject tofrequent failures. Another disadvantage is that the friction against thewalls of the hole causes the drill pipe to wind up with the result thata substantial amount of bouncing of the bit occurs on the bottom of thehole. This aggravates the wearing of the cutter hearings in rock bits.Thus, this is not an efiicient Way to induce alternate stresses of themagnitude and frequency required for eflicient use of the mechanism offatigue failure in the drilling operation. Thus, the present inventionis concerned with a device adaptable for use on the conventional rotarydrilling rig which provides for subjecting the rock to cyclic stresses.When operating in accordance with the present invention, induced failureof the rock by fatigue is St cured which promotes more rapid drillingwith less wea on the bit and accompanying equipment. The presetinvention may be more fully understood by reference t the drawingsillustrating embodiments of the same.

Figure 1 illustrates one adaptation of the circulatin pellets used inconjunction with a rock bit, while Figure 2 illustrates a similarapparatus except that a:

inercior cylindrical guide element for the pellets is pro W e Referringspecifically to Figure 1, the drill bit assembl is shown attached to thelower end of a drill string 1' disposed at the bottom of a well bore 11.The drill bi assembly is attached to the lower end of the drill strin,10 by threaded or equivalent means. The drill bit as sembly comprises acylindrical body element 3 havin, at its upper end a restricted nozzle 5communicating wit] the inside of the drill string. The lower end of thedril bit body 3 comprises a heavy percussion or plate ele ment 2.

The percussion or plate element 2 is attached to bi assembly 20 and thelatter has two rollers 21 and 21 at its lower end. Cylindrical bodyelement 3 is alsi characterized by having outlet ports 7 at the topshoulder thereof. The percussion or head element 2 is also characterized by containing a plurality of ports or jets 6 whicl permit thefluid to pass downwardly through the bit.

In operation, drilling fluid is pumped down within thl drill string 10.This fluid passes from the drill strin; through the restricted nozzle 5and picks up in the fluii stream pellet elements 4. These pellets arehard, metal lic alloys, as for example, various ferrous alloys. Tht sizeof the pellets may vary from about A inch to 1 incl and larger indiameter. These pellets impinge upon lht percussion element 2 at arelatively high velocity an then rebound outwardly and flow upwardlyalong tht inner side of the cylindrical body element. Approxi mately50-75% and more of the drilling fluid pumper down the drill stem passesthrough the port elements 6 This drilling mud passes downwardly throughthe bi and upwardly in the area between the outer surface 01 cylindricalbody element 3 and the wall of the well bore The remaining drillingfluid passes upwardly througt ports 7. The upflowing pellets arerepicked up by' the downflowing stream at nozzle 5 and again flow downwardly and impinge on the percussion element.

Referring specifically to Figure 2, the construction is identical withthat described with respect to Figure 1 except that an inner open-endedcylindrical conduit element 8 is concentrically disposed within the bodyelement 3 and supported by means of web members 25 that in turn aresecured to body element 3. In operation, the pellets 4 flow downwardlythrough conduit element 8, impinge on the head element 2, rebound andflow upwardly in the area between the inner wall of the body element andthe outer surface of the cylindrical element.

The present invention is broadly concerned with a mechanism andapparatus for producing a resonant action of the drill bit in a rotarydrilling operation, par ticularly when utilizing a rock bit. Inaccordance with the present invention, this is secured by theutilization of circulating pellets which impinge on a head plate whichis attached directly above the bit.

The rolling of the toothed cutters of the bit on the rock imparts to theresonant drill collar axial impact loads.

What is claimed is:

1. Improved drill bit assembly designed to be attached to the lower endof a drill string which comprises a roller type bit, a perforatedpercussion element positioned above said bit, a pellet chamberpositioned above said percussion element, conduit means for jetting astream of fluid from said drill stem into said chamber and pelletswithin said chamber adapted to be circulated by said jetted fluid so asto impart shocks to said percussion element, Whereby a pulsing motion isimparted to said bit.

2. Apparatus as defined by claim 1 wherein a hollow open-endedcylindrical element is concentrically disposed within said chamber, saidcylindrical element being spaced from the interior surfaces of saidchamber and supported therefrom by means of web members.

3. An improved rotary drill bit assembly designed to be attached to thelower end of a drill string which comprises in combination a hollow,cylindrical body member; a roller-type rotary bit mounted on the lowerend of said body member; a perforated percussion plate within said bodymember; said percussion plate being attached to the body member andforming a pellet chamber with the interior surfaces of said body member;a plurality of hard metallic pellets within said chamber; and conduitmeans arranged to jet fluid within said pellet chamber from said drillstring and to circulate said pellets within said chamber whereby thepellets impinge upon said perforated plate and transmit pulsing shocksto said rotary bit.

4. An improved rotary drill bit assembly for drilling bore holes anddesigned to be attached to the lower end of a drill string whichcomprises in combination a hollow, cylindrical body member attached tothe lower end of said drill string, said cylindrical body element beingcharacterized by having a restricted fluid passageway at its upper endcommunicating with the inside of said drill string, said body memberalso being characterized by containing a plurality of fluid ports at itsupper end communicating with the area between said drill string and thesurrounding bore hole, said body member further being characterized byhaving a lower percussion impact surface, a plurality of hard metallicpellets within said body member, said percussion surface containing apinrality of ports communicating with the interior of said body memberand the area below said body member, and a roller-type rotary bitattached to the lower end 0t said body member.

5. An apparatus for drilling bore holes which comprises in combination astring of drill pipe; a hollow, cylindrical body member attached to thelower end of said drill string; a jet passageway interconnecting theinterior of said body member with the interior of said drill string; aplurality of hard metallic pellets within said body member; means fortransporting a fluid through said drill string and thence through saidjet passageway into said body member; a percussion plate forming thebottom of said body member; and a roller type rotary drill bit attachedto the lower end of said body member, the percussion plate beingperforated to provide fluid passageways from the interior of said bodymember to said rotary bit.

References Cited in the file of this patent UNITED STATES PATENTS

